3-7 roadway_materials

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Roadway Materials The choice of roadway materials can have significant impacts on traffic safety, user comfort, vehicle maintenance costs, stormwater management, roadway noise, and the urban heat island effect. Designs must be carefully considered to ensure that they respond effectively roadway type, traffic loads, user mix, adjacent land uses, and the stormwater management context. Key dimensions include smoothness, durability, porosity, and color.

The design treatments on the following pages should be applied based on engineering judgment and in consultation with BTD. The guidance in this document should be supplemented with design guidance provided in the Manual on Uniform Traffic Control Devices, the MassDOT Project Development and Design Guide, and AASHTO Greenbook.

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More specific design guidance on roadway materials is provided on the following pages.

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Pavement Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Permeable Roadway Design. . . . . . . . . . . . . . . . . . . . . . . . .105 Colored Pavement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106

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Pavement Design

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Overview

Use

Effective pavement design responds to roadway context.

Factors to consider include heavy vehicle traffic, stormwater run-off, reflectivity, recycled content, and presence of underground utilities.

>> Pavements that resist shoving and rutting should be used for locations where heavy vehicles, such as heavy trucks or buses, stand or park, or locations that are particularly susceptible to wear, such as high-volume intersections or steep grades. Examples include concrete, reinforced concrete, and stone matrix asphalt. >> Pavement design should take into account the reflective characteristics of the pavement. High albedo content concrete and asphalt mixes absorb less heat and can help reduce the urban heat island effect. >> Pavement design should take into account the degree to which recycled materials can be used. Pavement mixes that include recycled content often perform as well as or better than pavement mixes that do not include recycled content. >> Pavement designs should meet ADA accessibility guidelines.

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Shared Streets Neighborhood Connector Boulevard Parkway

Considerations >> Concrete is discouraged where frequent utility cuts are likely. >> Concrete must have joints to allow for expansion. >> Epoxy coated, hot-dip galvanized, or stainless steel rebar should be used in reinforced concrete to prevent corrosion. >> Snow removal operations should be carefully considered where permeable pavements are used. Plow blades may need to be adjusted in order to avoid damaging the material, and the use of sand or ash should be avoided, because it will clog the pavement’s pores.

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>> Lifecycle costs are an important consideration in determining the appropriate pavement design.

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Permeable Roadway Materials

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Overview

Use

Permeable roadway materials accommodate pedestrian, bicycle, and vehicular traffic while serving a stormwater management function. With proper installation and maintenance, pervious pavement can infiltrate up to 80% of annual runoff volume, and can remove more than 60% of undissolved nutrients and 90% of sediment runoff.

>> Permeable paving materials are generally more appropriate for low-volume, low-speed roadways. However, roads with moderate or high vehicular flows may be designed to include permeable paving materials at locations where traffic is low, such as shoulders and parking lanes. >> The use of permeable paving materials must be part of an overall on-site management system for stormwater, and is not a replacement for other techniques. >> The aggregate base of a permeable roadway should be deep enough to ensure that water does not accumulate within the top-most pervious grade. >> In general, permeable pavements should only be used on roadways with slopes of 5% or less, due to the potential for water to seep out on steeper slopes. >> Permeable paving materials used at pedestrian crossing locations must meet ADA accessibility guidelines.

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Permeable roadway materials come in four basic varieties: >> Loose aggregate (gravel) >> Porous asphalt or concrete >> Open joined and open cell paving blocks with opening filled with porous aggregate or turf >> Plastic grid systems covered with soil and grass or gravel

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Considerations >> Proper installation and maintenance is critical. Applications of permeable pavement will require a maintenance agreement. >> Snow removal operations must be carefully considered.

Plow blades may need to be adjusted in order to avoid damaging the material. The use of sand or ash should be avoided, because it will clog the pavement’s pores.

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>> The characteristics of the each site must be carefully considered before applying permeable pavements. Important issues include the drainage characteristics of the underlying soils, the depth of the water table, and the slope of adjacent land.

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Colored Pavements

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Overview

Shared Streets Neighborhood Connector Boulevard Parkway

Use

Colored pavements can be used in the roadway to indicate modal priority/exclusiveness, increase awareness at potential conflict points, or provide directional guidance. Examples include crosswalks, bicycle lanes, cycle tracks, bus lanes, taxi lanes, hazardous curves, lane guidance at intersections, and restricted parking locations.

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Colored pavements can be made of a variety of materials.

Basic categories include paint, thermoplastic, and high-friction surfaces. Each category is accompanied by a different set of costs and benefits. Paint is the least expensive to install but is slippery and very susceptible to wear. Thermoplastic is more expensive than paint to install, but is not as slippery and lasts longer than paint under similar conditions. High-friction surfaces can be very durable and provide good traction but are very expensive to install (e.g., TyreGrip must be applied by hand).

>> The use of colored pavements for traffic control purposes (i.e., to communicate a regulatory, warning, or guidance message) is narrowly circumscribed by the MUTCD, which allows them only in conjunction with raised medians and channelization islands. All other traffic control applications should follow FHWA’s experimentation process. >> Colored pavement should be used consistently and be accompanied by interpretive signage. >> Careful consideration should be given to ensure that the type of material used is appropriate to the site and application.

Considerations >> Lifecycle costs are a key consideration for colored pavements. Factors to consider include material cost, installation cost, maintenance cost, and material degradation rate.

Paint applications may need to be maintained annually while high-friction applications may last up to 5 years. >> Durability is significantly influenced by weather conditions, pavement conditions, and other factors at the time of installation.

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